Functional substrate for controlling pixels

ABSTRACT

A functional substrate for controlling pixels, comprising; 
     a) a substrate; 
     b) an insulating film provided on said substrate; 
     c) a stripe-shaped transparent conductive film provided in plurality on said insulating film; 
     d) an opaque conductive film covered with said insulating film, arranged in parallel to said stripe-shaped transparent conductive film, and disposed between two stripe-shaped transparent conductive films adjacent to each other; and 
     e) a contact area at which one of said two stripe-shaped transparent conductive films adjacent to each other and said opaque conductive film are electrically connected.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a functional substrate provided with acolor filter, which is used in a color liquid crystal display, inparticular, a color ferroelectric liquid crystal display as a displaydevice, or in a color image pickup unit as an input device.

2. Related Background Art

Hitherto well known are liquid crystal devices in which scanningelectrodes and signal electrodes are formed in a matrix fashion and thespaces between the electrodes are filled with liquid-crystal compoundsto form a large number of picture elements (pixels) so that an image orinformation can be displayed. Employed as a system of driving suchdisplay devices is time-sharing drive wherein address signals areselectively applied to the scanning electrodes in a successive andperiodic fashion and given information signals are selectively appliedto the signal electrodes in a synchronous and parallel fashion to theaddress signals.

In recent years, aiming at making larger the screen of liquid crystaldisplay units, it is progressed to use the surface-stabilizedferroelectric liquid crystal devices disclosed, for example, in U.S.Pat. Nos. 4,367,924 and 4,639,089. As the screen is made larger, thescanning electrode and signal electrode of the matrix electrode havebecome increasingly long, so that the effect of delaying an appliedvoltage (or applied-voltage delay effect) has brought about a seriousproblem.

Conventional TN (twisted nematic) liquid crystal devices or STN (supertwisted nematic) liquid crystal devices employ multiplexing drive inwhich the applied voltage is periodically applied (namely, a singlepicture with a high contrast is formed by plural-frame scanning), andhence the lowering of display quality level, ascribable to theapplied-voltage delay effect mentioned above, has been littlequestioned. In the instance of the ferroelectric liquid crystal device,however, a single picture with a high contrast must be formed bysingle-frame scanning, so that the applied-voltage delay effectmentioned above has brought about a serious problem. Heat generationaccompanying wiring resistance is also incidental to such a delay effectto cause a non-uniformity of temperature distribution in cells,resulting also in a lowering of display quality level.

For the foregoing reasons, in applying the ferroelectric liquid crystaldevice to a large screen display panel, a method has been employed inwhich a metallic film or an alloy film is wired in contact in thelongitudinal direction of the scanning electrode and signal electrode sothat the applied-voltage delay effect can be suppressed or eliminated.In an instance in which the above delay effect is suppressed by usingthick-wall transparent electrodes as the scanning electrode and signalelectrode, the transmittance in a light state is also lowered, resultingin a low contrast and low brightness of the picture.

Incidentally, as having been made clear in the U.S. Patents set outabove, in embodying the surface-stabilized ferroelectric liquid crystaldevice, the space between substrates is required to be set with adistance small enough to suppress the specific spiral arrangementstructure of a ferroelectric smectic liquid crystal and give a bistablyoriented state, i.e., a distance of usually from 0.1 μm to 3 μm inapproximation.

Experiments made by the present inventors revealed that the filmthickness of a low-resistivity conductive film used for suppressing theapplied-voltage delay effect, which is used when the surface-stabilizedferroelectric liquid crystal device is applied to a large screen displaypanel, may be brought into a thick-wall state of not less than 0.1 μm,and preferably not less than 0.5 μm, thereby making it possible tobetter preventing the lowering of display quality level, ascribable tothe delay effect.

However, the wiring of the above thick-wall low-resistivity conductivefilm in contact with the transparent electrodes has brought about theproblem that a danger of a short between the upper and lower substratesincreases at the part such wiring is made. In a display screen,existence of even only one shorted part can be found by a viewer, thusmaking a serious problem from the viewpoint of the display qualitylevel.

In the ferroelectric liquid crystal device, rubbing is applied on thesurface of the substrate so that liquid crystal molecules may bearranged in a given direction. In applying this rubbing, there has beenthe problem of a phenomenon that the protruded part of thelow-resistivity conductive film causes peeling.

In color display using a liquid crystal display panel, a color filterfor full colors that employs an integrated body of fine microfilters forR (red), G (green) and B (blue) is provided on the liquid crystaldisplay panel so that the color display can be reproduced using lightrays passed through the liquid crystal display panel capable of opticalswitching with the color filter.

Color filters used for such purpose are disclosed, for example, inJapanese Unexamined Patent Publications No. 57-16407, No. 57-74707, No.60-129707, No. 62-212603 and No. 62-218902.

In the above prior art, however, the following problems have beeninvolved from the viewpoints of fabrication processes and colorreproducibility.

(1) In the process of forming a colored resin layer, exposure to lightis carried out using a photomask, with alignment at the desiredposition. However, there is a limit in the alignment precision, andhence it often occurs that a gap is made between the color resin layerand a light-screening layer or that the colored resin layer is formedoverlapping on the light-screening layer. This gap results in a loweringof contrast in the case of liquid crystal display devices. In the caseof image pickup devices, on the other hand, a flare phenomenon is causedto make an image difficult to view. The overlapping between thelight-screening layer and colored resin layer may also give cell gapirregularities in the case of liquid crystal display devices to causeorientation disturbance, resulting in a lowering of the display qualitylevel.

(2) In order to cure the colored resin in the process of forming thecolored resin layer, the exposure is carried out from the surface.Hence, the photo-curing sufficiently takes place at the area near to thesurface but insufficiently at the interface with the substrate, so that,at the time of developing, cracking and turning-up and peeling ofpatterns tend to occur, and the stability of the process can be by nomeans well satisfactory.

(3) In instances in which a material having a high reflectance (asexemplified by a metal) is used in the light-screening layer when thesurface exposure is made, a photosensitive colored resin film on thelight-screening layer may be cured with a great influence of the lightthat reflects around as a result of the exposure, making it difficult tocarry out development.

(4) In the above prior art, all instances essentially require theoperation of alignment between the formation of a color filter patternand the formation of a non-light-transmissive film pattern. Hence, therehas been the problem that the influence on the precision of thisalignment makes it difficult to form between color filter patterns anon-light-transmissive film pattern free of any light-transmissive areaand coincident in size. When the overlapping has occurred between these,there also has been the problem that a faulting (a difference in level)made on the color filter makes it difficult to form a color filterhaving a structural strength and an excellent flatness.

The above four points have been serious problems from the viewpoints offabrication processes and color reproducibility.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a functional substratethat has solved the above problems, and also provide a functionalsubstrate using a color filter that can be used in color display devicesor image pickup devices.

Another object of the present invention is to provide an opticalmodulator that has solved the above problems, and, in particular, asurface-stabilized ferroelectric liquid crystal device capable ofsuppressing a short from occurring.

The present invention can be achieved by a functional substrate forcontrolling pixels, comprising;

a) a substrate;

b) an insulating film provided on said substrate;

c) a stripe-shaped transparent conductive film provided in plurality onsaid insulating film;

d) an opaque conductive film covered with said insulating film, arrangedin parallel to said stripe-shaped transparent conductive film, anddisposed between two stripe-shaped transparent conductive films adjacentto each other; and

e) a contact area at which one of said two stripe-shaped transparentconductive films adjacent to each other and said opaque conductive filmare electrically connected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section of an electrode substrate used in the presentinvention;

FIG. 2 is a perspective view thereof;

FIG. 3 is a cross section of another electrode substrate used in thepresent invention;

FIG. 4 is a cross section of a liquid crystal device of the presentinvention;

FIG. 5 is a perspective view of a ferroelectric liquid crystal device;

FIG. 6 is a perspective view of a surface-stabilized ferroelectricliquid crystal device in a bistably oriented state;

FIGS. 7 (7A to 7J) to 11 (11A to 11G) cross-sectionally illustrateprocesses of forming the color filter of the present invention;

FIG. 12 is a cross section of a liquid crystal display panel in whichthe functional substrate of the present invention is employed;

FIG. 13 (13A to 13H) is a process of forming a thin-film transistorarray used in the present invention;

FIG. 14 is a diagrammatical plan view of a photosensor array used in thepresent invention;

FIG. 15 (15A to 15G) is a process of forming the photosensor array usedin the present invention; and

FIGS. 16 (16A to 16G) and 17 (17A to 17E) cross-sectionally illustrateprocesses of forming the color filter of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a cross section of the substrate used in the presentinvention, and FIG. 2 is a perspective view thereof. In FIGS. 1 and 2,the numeral 14 denotes a substrate, for which a glass sheet or plasticsheet is used. The numeral 11 denotes a transparent electrode of 100 Åto 5,000 Å thick, formed of a transparent conductive film (made of, forexample, indium oxide, tin oxide, indium-tin oxide: ITO), and is used asa scanning electrode or signal electrode in the multiplexing drive. Thistransparent electrode 11 is provided on insulating film 13 formed on thesubstrate 14.

In the present invention, low-resistivity electrode 12, comprising aconductive film formed by vacuum deposition or sputtering of a metalsuch as aluminum, chromium, gold, silver, copper, molybdenum andtungsten, or an alloy thereof, is formed on substrate 14. Thislow-resistivity electrode 12 is electrically connected to transparentelectrode 11 in its longitudinal direction through a through-hole formedin insulating film 13.

In this constitution, low-resistivity electrode 12 can also function asa light-screening film when it is disposed between transparentelectrodes 11 adjacent to each other, in the manner that it covers thespace between the electrodes. In regard to the ferroelectric liquidcrystal present at the space between transparent electrodes 11 (whichcorresponds to a non-picture element area), the direction of orientationof liquid crystal molecules can not be controlled by an applied voltage,and hence the state of orientation at the initial orientation stage ismaintained as it is. Thus, because of the liquid crystal oriented in twodifferent molecular axes in the initial orientation state of theferroelectric liquid crystal, the light domain and dark domain aremixedly present to bring about the problem of the breaking-through oflight. However, the employment of low-resistivity electrode 12 to whichthe light-screening function as mentioned above is imparted has settledsuch a problem. Moreover, even when compared with a conventionalconnecting method, the effective display area is not decreased.

Low-resistivity electrode 12 used in the present invention should have afilm thickness of not less than 0.1 μm, and more preferably from 0.5 μmto 5 μm, in approximation so that it can sufficiently suppress theapplied-voltage delay effect previously mentioned when the device isused in the large screen display panel. The surface of low-resistivityelectrode 12 can also be applied with a reflection preventive treatment,and thus it is possible to prevent the light reflecting from the spacesbetween picture elements (i.e., the non-picture element areas).

When low-resistivity electrode 12 and transparent electrode 11 areelectrically connected through the through-hole of insulating film 13,the contact width thereof should also be as large as possible. The widthmay be about 10 μm in the instance where transparent electrode 11 iswired in a stripe form.

Insulating film 13 can be provided by coating such as spin coating orroll coating, or vacuum deposition, of organic resins such as polyamide,polyimide, polyvinyl alcohol, polyurethane, polycarbonate or siliconeresins, or inorganic materials such as Si₃ N₄, SiO₂, SiO, Al₂ O₃ and Ta₂O₃. In a preferred embodiment of the present invention, insulating film13 having been formed into a film may preferably be leveled tolow-resistivity electrode 12. For such purpose, the film thickness ofinsulating film 13 covered on the substrate 14 on which low-resistivityelectrode 12 is absent may be set to be approximately not less than 1.5,and preferably from 2 to 10, times the film thickness of low-resistivityelectrode 12, so that the film thickness of insulating film 13 coveredon substrate 14 can be leveled over the whole area. Suited as filmformation methods usable in that instance is the spin coating or rollcoating of organic resins, previously described. On this insulating film13, a through-hole is also formed which enables electrical connectionbetween transparent electrode 11 on insulating film 13 andlow-resistivity electrode 12 below insulating film 13.

The numeral 15 in FIG. 2 denotes an opposed electrode provided on anopposed substrate (not shown), and the part at which this opposedelectrode 15 and transparent electrode 11 cross serves as pictureelement region 10.

Electrode substrate 1 shown in FIG. 1 and FIG. 2 can be provided with anorientation control film, formed into a film, using, for example,inorganic insulating materials such as silicon monoxide, silicondioxide, aluminum oxide, zirconium oxide, magnesium fluoride, ceriumoxide, cerium fluoride, silicon nitride, silicon carbide, and siliconboride, or organic insulating materials such as polyvinyl alcohol,polyimide, polyamidoimide, polyesterimide, polyparaxylylene, polyester,polycarbonate, polyvinyl acetal, polyvinyl chloride, polyamide,polystyrene, cellulose resin, melamine resin, urea resin, and acrylicresin. This orientation control film can also be formed on an additionalinsulating film of 500 Å to 1 μm thick provided on transparent electrode11.

This orientation control film can be obtained by rubbing its surface inone direction using velvet, cloth or paper, after the inorganicinsulating material or organic insulating material as previouslydescribed has been formed into a film.

In another preferred embodiment of the present invention, theorientation control film can be obtained by forming the inorganicmaterial such as SiO or SiO₂ into film by oblique vacuum deposition onelectrode substrate 1.

The orientation control film described above can be formed with athickness of usually from 10 Å to 1 μm. In the instance in which it isdirectly provided on transparent electrode 11, however, it should beformed with a thickness of from 500 Å to 1 μm, and, in the instance inwhich it is formed on an insulating film additionally formed ontransparent electrode 11, a thickness of approximately from 10 Å to 500Å.

FIG. 3 is a cross section of color electrode substrate 3 used in thepresent invention. Color electrode substrate 3 in FIG. 3 comprises bluecolor filter 31B, red color filter 31R and green color filter 31Gprovided on substrate 14, and the previously described low-resistivityelectrode 12 is disposed between the individual color filters adjacentto each other, of color filter 31. On color filter 31 andlow-resistivity electrodes, the insulating film 13 is provided in thesame manner as previously described. This insulating film 13, however,can also function as a protective film for color filter 31. Then, likethe previously described, low-resistivity electrode 12 is electricallyconnected to transparent electrode 11 through a through-hole formed ininsulating film 13. The orientation control film previously describedcan also be provided on color electrode substrate 3.

Color filter 31 should be formed with a thickness of from 0.1 μm to 5μm, and preferably from 0.5 μm to 2 μm, and particularly formed bydispersing a pigment or dye in a resin. Resin materials used on thatoccasion can be preferably selected from gelatin, casein, glue,polyvinyl alcohol, polyimide, polyamidoimide, polyesterimide,polyparaxylylene, polyester, polycarbonate, polyvinyl acetal, polyvinylchloride, polyvinyl acetate, polyamide, polystyrene, cellulose resin,melamine resin, urea resin, acrylic resin, epoxy resin, photosensitivepolyamide photoresists, photosensitive polyamide photoresists, cyclizedrubber photoresists, phenol novolac photoresists, and electron rayphotoresists [such as acrylate or methacrylate (monomers, oligomers, orprepolymers) and epoxidated 1,4-polybutadiene]. The pigment or dye usedon that occasion also includes those of an azo type, an anthraquinonetype, a phthalocyanine type, a quinacridone type, an isoindolinone type,a dioxazine type, a perylene type, a perynone type, a thioindigo type, apyrocholine type, or a quinophthalone type.

Insulating film 13 used in color electrode substrate 3 is required tohave together the function as a protective film, and therefore should beselected particularly from films formed by coating such as spin coatingor roll coating of organic resins such as polyamide, polyimide,polyurethane, polycarbonate or silicone resins, or inorganic materialssuch as Si₃ N₄, SiO₂, SiO, Al₂ O₃ and Ta₂ O₃.

FIG. 4 is a cross section to show a liquid crystal device of the presentinvention. The liquid crystal device shown in FIG. 4 comprisessurface-stabilized ferroelectric liquid crystal 42 kept in a bistablyorientated state, provided between two sheets of electrode substrates 1Aand 1B. The space between the two substrates is set with a distancesmall enough to suppress the spiral arrangement structure of aferroelectric liquid crystal that gives a bistably oriented state of thespiral arrangement structure in a bulky state, e.g., a distance ofusually from 0.1 μm to 3 μm. This space with a small distance is kept byspacer material 44 such as silica beads, alumina beads, glass fiber andplastic beads.

The two sheets of electrodes substrate 1A and 1B are, as illustrated inFIG. 4, respectively provided with substrates 14A, and 14B, insulatingfilms 13A and 13B, low-resistivity electrodes 12A and 12B, transparentelectrodes 11A and 11B (transparent electrodes 11A and 11B arerespectively formed in stripes to give matrix electrodes crossing eachother at angles of 90° C.), and orientation control films 41A and 41B.The orienting treatment axes formed on orientation control films 41A and41B provided on electrode substrates 1A and 1B should preferably be inthe direction parallel to each other. The orienting treatment axes usedhere may be given by monoaxial molecular aligning treatment such asrubbing or oblique vacuum deposition as previously described.

For the purpose of optically detecting the orientation modulation ofliquid crystal molecules, polarizers 43A and 43B are disposed on bothsides of the two sheets of electrode substrates 1A and 1B, respectively,in crossed nicols.

FIG. 5 diagramatically illustrates an example of a cell to describe theoperation of a ferroelectric liquid crystal. The numerals 51A and 51Bare substrates (glass sheets) each covered with a transparent electrodecomprised of a thin film of In₂ O₂, SnO₂, ITO or the like, between whicha liquid crystal of an SmC* (chiral smectic phase C) phase or SmH*(chiral smectic H) phase, whose liquid crystal molecular layer 52 is sooriented as to be perpendicular to the glass surface is hermeticallysealed. The line shown by a thick line represents a liquid crystalmolecule, and this liquid crystal molecule 53 has bipolar moment (P⊥) 54in the direction crossing at right angles to its molecule. Applyingbetween substrates 51A and 51B a voltage of not lower than a giventhreshold value makes loose the spiral structure of liquid crystalmolecule 53, and thus the orientation direction of liquid crystalmolecule 53 can be changed so that all bipolar moments (P⊥) 54 may facethe direction of the electric field. Liquid crystal molecule 53 is longand slender in its shape, and shows the refractive index anisotropy inits major axis direction and minor axis direction. Thus, it can bereadily understood that, if, for example, polarizers each other arrangedin crossed nicols are placed above and below the glass surface, there isgiven a liquid crystal optical modulation device that changes itsoptical properties depending on the polarity in voltage application.

The surface-stabilized ferroelectric liquid crystal cell kept in thebistably oriented state, preferably used in the optical modulationdevice of the present invention, can be made to have a sufficientlysmall thickness (for example, of from 0.1 μm to 3 μm). As the thicknessof a liquid crystal layer becomes small like this, the spiral structureof the liquid crystal molecues becomes loose even in the state in whichno electric field is applied, and they turn to have a non-spiralstructure as illustrated in FIG. 6, where its bipolar moment P or P'takes the state of either upward direction (64A) or downward direction(64B). When such a cell is applied with electric field Ea or Eb havingdifferent polarity and of not lower than a given threshold value asshown in FIG. 6, using voltage applying means 61A and 61B, the bipolarmoment changes its direction upward 64A or downward 64B corresponding tothe electric field vector of electric field Ea or Eb, and, in accordancewith it, the liquid crystal molecules orient to any one of first stablestate 63A or second stable state 63B.

The effect obtainable by this ferroelectric liquid crystal cell is, inthe first place, that it shows a very high response speed, and, in thesecond place, that the alignment of liquid crystal molecules arebistable. To further detail the second point with reference to FIG. 6,the application of the electric field Ea results in the alignment ofliquid crystal molecules in first stable state 63A, which state,however, is stable even after the electric field has been turned off.The application of the reverse electric field Eb also results in thealignment of liquid crystal molecules in second state 63B with thechange of the molecular direction, which state, however, is also kepteven after the electric field has been turned off. The respectiveoriented state are also maintained so long as the electric field Eaapplied does not exceed a given threshold value.

The ferroelectric liquid crystal used in the present invention mayinclude various types, but may preferably be a chiral smectic liquidcrystal commonly having the temperature range that can produce thecholesteric phase and smectic A phase in the course the temperature islowered. Stated specifically, "CS-1011", "CS-1014", "CS-1017", "CS-1018"(all trade names for Chisso Corporation), etc. are used.

The method of forming the color filter according to the presentinvention is a method in which, using a light-screening layer as themain mask, the back side of a substrate, having been roughly alignedwith a photomask (rough mask), is subjected to the back-side exposure tobring the desired area of a photosensitive colored layer into photocure,thus forming a film insoluble to a developing solution, followed byremoval of an unexposed area as a result of developing, to obtain acolored pattern. Description will be specifically made below withreference to FIG. 7 (7A to 7J).

As shown in FIG. 7A, light-screening film 72 is provided on substrate71, and then a pattern is formed using photoresist 76. Here, substrate71 must be a substrate made of glass or the like, capable oftransmitting light of from 300 nm to 400 nm. The light-screening filmdenoted as 72 may preferably be a film having a transmittance of notmore than 2% at 300 nm to 800 nm. Next, the insoluble area of thelight-screening film is removed by etching and thereafter thephotoresist is also removed. Used as a means for removing thislight-screening film is wet etching, dry etching, or the like. In thecase when the light-screening film is formed by vacuum deposition,lifting-off is also an effective means. As a result, light-screeningfilm pattern 72a as shown in FIG. 7B is obtained. Then, the wholesurface is coated with photosensitive colored resin 73 (red) as shown inFIG. 7C. A base resin material for the photosensitive colored resinincludes gelatin, casein, glue, polyvinyl alcohol, polyimide,polyamidoimide, polyesterimide, polyparaxylylene, polyester,polycarbonate, polyvinyl acetal, polyvinyl chloride, polyvinyl acetate,polyamide, polystyrene, cellulose resin, melamine resin, urea resin,acrylic resin, and epoxy resin. A pigment or dye mixed in the resinincludes those of an azo type, an anthraquinone type, a phthalocyaninetype, a quinacridone type, an isoindolinone type, a dioxazine type, aperylene type, a perynone type, a thioindigo type, a pyrocholine type,or a quinophthalone type.

Then, in order to expose only the desired area to light, photomask 77 isaligned on the back side of substrate 71, and thus exposure is carriedout from the back side. As a result, the desired area only isphoto-cured to turn insoluble to a developing solution. Photomask 77used here has less influence on the precision of the filter pattern evenif it is aligned with some deviation. This is because edge areas areprecisely exposed to light by virtue of light-screening film pattern72a. Then, the unexposed area is dissolved and removed as a result ofdeveloping, and thus a colored pattern of a first color is obtained asshown in FIG. 73D. A second color pattern and a third color pattern arealso similarly formed to obtain a color filter of three colors as shownin FIG. 7H. If necessary, a passivation layer 78 as shown in FIG. 7I isfurther provided. In particular, in the instance of a liquid crystalcolor display panel, it is also effective for driving a liquid crystaldevice to form light-screening film pattern 72a with a metal (asexemplified by aluminum), and connecting it with ITO on passivationlayer 78 to lower the resistivity.

Thus, it has become possible to form a color filter having no gapbetween the filter and light-screening film and also being free of thefaulting (difference in level) due to the overlapping between thelight-screening film and filter.

EXAMPLE 1 Color filter for liquid crystal display

An example according to the present invention will be described withreference to FIG. 7 (7A to 7J).

As shown in FIG. 7A, aluminum is provided by sputtering with a filmthickness of 1.5 μm on glass substrate 71, and thereafter a pattern formaking stripes of 100 μm wide is formed using a positive resist(HPR-1182; a product of Fuji-Hunt Electronics Technology Co.). Then thealuminum at the area not protected by the resist is removed using analuminum etching solution, thereby forming colored layer openings asshown in FIG. 7B. Thereafter the resist layer is removed using acetone.Then, as shown in FIG. 7C, red colored layer (continuous film) 73(Red)of 1.5 μm thick is formed on the whole surface by spin coating of adispersion comprising a red pigment dispersed in a photosensitivepolyamide resin, followed by pre-baking at 90° C. for 30 minutes.Thereafter, the back side of a glass substrate is aligned with aphotomask, and the back-side exposure is carried out using an energy of3,000 mJ/cm² to bring the photosensitive colored resin on the glasssurface between aluminum light-screening films 72a into photocure, thusforming a film insoluble to a developing solution. Then the unexposedarea is dissolved and removed using a developing solution exclusivelyused therefor, followed by post-baking at 200° C. for 30 minutes. Redcolored layer 73(Red) as shown in FIG. 7D is thus obtained. Greencolored layer 74(Green) and blue colored layer 75(Blue) are alsosimilarly formed (FIG. 7H). Then, as shown in FIG. 7I, passivation layer78 is formed (using PI-300; a product of Ube Industries, Ltd.) with athickness of 1.5 μm on the colored layer, and thereafter ITO (indium-tinoxide) is provided thereon by sputtering with a thickness of 2,000 Å,followed by patterning according to photolithoetching. Resulting ITOfilm 79 is in contact with the aluminum serving as light-screening film72a. This contact of aluminum with ITO brings about a lowering of theresistivity of the electrode.

EXAMPLE 2 Color filter for image pickup device

Another example will be described with reference to FIG. 8 (8A to 8E).

As shown in FIG. 8A, colored film 80 (available from Fuji-HuntElectronics Technology Co.; a color mosaic system, black) is provided byspin coating on glass substrate 81, followed by pre-baking at 100° C.for 15 minutes. Thereafter, using photomask 87a, the film is exposed tolight at an energy of 40 mJ/cm² using ultraviolet rays, thus forming afilm soluble to a developing solution. Then the exposed area isdissolved and removed using a developing solution exclusively usedtherefor to form light-screening film pattern 80a as shown in FIG. 8B.Post-baking is then carried out at 180° C. for 30 minutes, andthereafter coating 83, a first color, comprising a red pigment dispersedin a photosensitive polyamide resin is formed on the whole surface byspin coating. Thereafter, pre-baking is carried out at 90° C. for 30minutes, and then the back side of the substrate is aligned withphotomask 87b to make back-side exposure at an energy of 3,000 mJ/cm²using ultraviolet rays. As a result, the desired area of red coloredlayer 83 is photo-cured to turn insoluble to a developing solution. Thenthe unexposed area is dissolved and removed using a developing solutionexclusively used therefor, followed by post-baking at 200° C. for 30minutes to form red colored layer 83 as shown in FIG. 8D. Green and bluecolored layers are similarly formed by repeating the procedure shown inFIGS. 8C and 8D. The colored layers each have a film thickness of 1.7 μm(red, 83), 1.5 μm (green, 84) and 1.9 μm (blue, 85).

Then passivation layer 88 is finally formed (using PI-300; a product ofUbe Industries, Ltd.) with a thickness of 1.0 μm. A color filter for animage pickup device as shown in FIG. 8E is thus formed.

As described in the above, since the colored layer is formed using thelight-screening layer as the first mask and the photomask as the secondmask, the light-screening layer and colored layer can be preciselyformed without any gap. Thus, in the case of liquid crystal displaypanels, no lowering of contrast occurs, which is due to blank areas,resulting in an improvement in the contrast. In the case of image pickupdevices also, no flare phenomenon is caused, and hence a sharp image canbe obtained.

The exposure is carried out from the back side of the substrate, so thatthe adhesion at the interface between the substrate and colored layer isimproved to make the process stable and at the same time improve theyield.

Particularly in the case of liquid crystal display panels, thelight-screening film or layer is used as a mask. Hence, no faulting(difference in level) is caused, which has been hitherto caused by theoverlapping of the light-screening layer and colored layer because ofthe alignment deviation, so that a uniform cell gap can be obtained.When the stripe pattern is formed using a metal, on the light-screeninglayer, the wiring resistance can be lowered as a result of itsconnection with the ITO layer formed later, so that it becomes possibleto lessen the heat generation on the panel or the waveform dullness.

Thus, the formation of the color filter, using the light-screening filmor layer as the mask and according to the back-side exposure can bringabout a good effect from the viewpoints of the stableness on the processand the color reproducibility.

Another embodiment of the present invention is in the first placecharacterized by a color filter comprising an aggregate of colormicrofilters arranged in parallel on a substrate, wherein alight-screening area set to have a thickness not more than twice thefilm thickness of said color microfilters is provided between said colormicrofilters. In the second place, the color filter can be prepared by amethod comprising;

a first step of forming on a substrate a first opaque film having beensubjected to patterning to a first pattern form;

a second step of providing a first photosensitive colored resin film onthe substrate having said first opaque film;

a third step of subjecting the first photosensitive colored resin filmformed in said second step, to exposure from the back side of thesubstrate, and removing the first photosensitive colored resin filmformed on the first opaque film;

a fourth step of forming a second opaque film having been subjected topatterning to a second pattern form, on the substrate having the firstcolored resin film having been subjected to patterning in said thirdstep and the first opaque film;

a fifth step of forming a second photosensitive colored resin film onthe substrate having said second opaque film; and

a sixth step of subjecting the second photosensitive colored resin filmformed in said fifth step, to exposure from the back side of thesubstrate, and removing the second photosensitive colored resin filmformed on the second opaque film.

First, in FIG. 9A, opaque film 92A that serves later as light-screeningfilm 92 is formed on a glass plate, substrate 91 of the color filter.Light-screening film 92 or opaque film 92A may be comprised of any metalor alloy, or colored resin, so long as it has the performance ofintercepting light, but may preferably be a low-resistivity film made ofa metal or alloy. Next, opaque film 92A at position 93A at which a firstcolor (red color) area corresponding to color microfilter 93 is formedis removed by a photolithoetching technique, so that glass surface 93Bat red area forming position 93A having been subjected to patterning canbe uncovered to the outside. In FIG. 9B, negative photosensitive coloredresin film 93C (red color) which is a material of red microfilter 93 isprovided on the whole surface by spin coating, followed by pre-baking.Then, exposure to ultraviolet light is carried out from the back side ofsubstrate 91, so that red photosensitive colored resin film 93C isexposed to light only at red area forming position 93A, and proceeds tocure by photo-crosslinking, turning insoluble to a developing solution.Thereafter, red photosensitive colored resin film 93C on opaque film 92Anot having been photo-crosslinked is removed using a developing solutionexclusively used therefor, followed by post-baking, thus obtaining afist color, red microfilter 93 as shown in FIG. 9C.

Next, a second color, green microfilter 94 is formed, where, however, anopaque film 96 must be formed as shown in FIG. 9D, using a materialdifferent from opaque film 92 initially used, in order that the secondcolor area may not be formed on the first color (red color) area.Accordingly, after second opaque film 96 has been newly provided on thewhole surface, second opaque film 96 formed at the second color, greenarea forming position 94A is removed by photolithoetching like the caseof the first color area, so that glass surface 94B is uncovered to theoutside. In FIG. 9E, green photosensitive colored resin film 94C isprovided by coating on the whole surface, and baked. Thereafter,exposure to ultraviolet light is carried out from the back side ofsubstrate 91, followed by developing, and then post-baking. A secondcolor, green microfilter 94 is thus formed as shown in FIG. 9F. A thirdcolor, blue microfilter 95 is obtained in the same manner as the case ofthe second color area. Namely, in FIG. 9G, opaque film 97 is provided inthe manner that the blue area forming position 95A is formed bypatterning and glass surface 95B is uncovered to the outside, andthereafter blue photosensitive colored resin film 95C as shown in FIG.9H is provided by coating, and baked. Thereafter, exposure usingultraviolet light is carried out from the back side of substrate 91,followed by developing, and then post-baking. The third color, bluemicrofilter 95 is thus formed as shown in FIG. 9I.

Subsequently, as shown in FIG. 9J, opaque films 96 and 97 is dissolvedand removed, so that color filter 9 can be obtained in which anaggregate of respective red microfilter 93, green microfilter 94 andblue microfilter 95 is arranged.

In the present invention, as shown in FIG. 9K, transparent insulatingfilm 98, which is a transparent resin film (comprising polyamide,polyester or polyolefin), is further formed on color filter 9, andcontact hole 98A is formed on light-screening film 92 of thistransparent insulating film 98 (here is used a film formed with alow-resistivity opaque film made of a metal, an alloy or the like) sothat light-screening film 92 may be electrically connected withtransparent conductive film (made of, for example, SnO₂, In₂ O₃, orindium-tin oxide) 99 serving as a transparent electrode, provided ontransparent insulating (passivation) film 98. FIG. 10 (10A to 10G)illustrates another preferred embodiment of the present invention. Theprocess shown in FIG. 10 is embodied by omitting opaque films 96 and 97used in the process of FIG. 9, and imparting the functions shared bythem to the color microfilters. Hence, the color microfilters used inthe present Example must be substantially opaque to the light of thephotosensitive wavelength region of the photosensitive colored resinfilm.

FIGS. 10A, 10B and 10C show the same steps as those in FIGS. 9A, 9B and9C (in this instance, red photosensitive resin film 93C is made to havea larger thickness than the film thickness of the opaque film 92A).Next, the green area forming position 94A as shown in FIG. 10D is formedby patterning, on which green photosensitive resin film 94C as shown inFIG. 10E is provided by coating. This green photosensitive resin film94C is exposed to light from the back side of substrate 91, and has nosubstantial sensitivity to ultraviolet light passed through redmicrofilter 93. Hence, after the exposure is carried out usingultraviolet light as shown in FIG. 10E followed by developing, greenmicrofilter 94 as shown in FIG. 10F is formed. Subsequently, a similarstep may be followed to form blue microfilter 95 as shown in FIG. 10G.Transparent passivation film 101 is further provided thereon by coating.In the present Example, it is preferred that the color microfilters areformed in the order of a green microfilter, a blue microfilter, and ared microfilter, and, as to the film thickness in forming these, the redmicrofilter is made to have the largest film thickness and the bluemicrofilter the smallest film thickness.

The photosensitive resin used in the present invention may preferablyinclude photosensitive polyamides, photosensitive polyimides, cyclizedrubber photoresists, and phenol novolac photoresists. In thisphotosensitive resin, a pigment or dye of an azo type, an anthraquinonetype, a phthalocyanine type, a quinacridone type, an isoindolinone type,a dioxazine type, a perylene type, a perynone type, a thioindigo type, apyrocholine type, or a quinophthalone type may be dispersinglycontained, so that there can be obtained a photosensitive resin coloredinto red, green or blue. The above color microfilters should be made tohave a film thickness of from 0.1 μm to 5 μm, and preferably from 0.5 to2 μm. In setting this film thickness, the color microfilters should bemade to have a film thickness of not more than twice, preferably from0.5 time to 1.5 times, and more preferably from 0.8 time to 1.2 timesthe film thickness of the light-screening film 92. A film thickness ofthe color microfilter, more than twice that of light-screening film 92may enable no sure masking at opaque film 92A serving as a mask, whenexposure to ultraviolet light is carried out from the back side ofsubstrate 91.

EXAMPLE 3 Preparation of color filter for liquid crystal display panel

The method of forming the color filter for a liquid crystal displaypanel according to the present invention will be described withreference to FIG. 9.

On glass substrate 91, an aluminum film serving as light-screening film92 was formed by sputtering so as to have a film thickness of 1.5 μm.Thereafter, a pattern for making stripes of 100 μm wide and pitch wasformed using a resist, and then the aluminum film was etched so thatglass surface 93B at red area forming position 93A as shown in FIG. 9Awas uncovered. Thereafter, a dispersion comprising a red pigmentdispersed in a photosensitive polyamide resin PA-1000 (a product of UbeIndustries, Ltd.), which is a material of the first color area, wasapplied on the whole surface by spin coating so as to give a filmthickness of 1.5 μm, followed by pre-baking (80° C., 30 minutes). Then,the whole areal exposure (3,000 mJ/cm²) was carried out usingultraviolet rays, from the back side of substrate 91 to cure only thecolored resin on the glass surface to bring it into a state insoluble toa developing solution. The colored resin on the aluminum film,corresponding to the unexposed area, was removed using a developingsolution exclusively used therefor, and rinsed with a rinsing solutionexclusively used therefor, followed by post-baking (200° C., 60 minutes)to form an aggregate of red microfilter 93 as shown in FIG. 9C. Next, toform a second color, green microfilter 94, a chromium film was providedby sputtering with a film thickness of 1,000 Å as opaque film 96 on thewhole surface for the purpose of preventing green microfilter 94 frombeing formed on red microfilter 93 first formed. Thereafter, thechromium film and aluminum film on green area forming position 94A weresubjected to patterning using a resist, and then removed by etching touncover glass surface 94B. Here, green area forming position 94A wasdistant by 5 μm from the end of red microfilter 93, with a pattern widthof 100 μm like that of the red microfilter 93 (FIG. 9D). Thereafter, adispersion comprising a green pigment dispersed in photosensitivepolyamide resin PA-1000 (a product of Ube Industries, Ltd.) was appliedon the whole surface by spin coating so as to give a film thickness of1.5 μm, followed by pre-baking (80° C., 30 minutes). Then, the wholeareal exposure was carried out at 5,000 mJ/cm² using ultraviolet light,from the back side of substrate 91 to cure only the green colored resinon the glass surface to bring it into a state insoluble to a developingsolution (FIG. 9E). The green colored resin on the chromium film,corresponding to the unexposed area, was removed using a developingsolution exclusively used therefor, and rinsed with a rinsing solutionexclusively used therefor, followed by post-baking (200° C., 60 minutes)to form green microfilter 94 as shown in FIG. 9F. Then, as shown in FIG.9G, a chromium film was formed so that a third color (blue color) areamay not be formed on green microfilter 94, and the chromium film andaluminum film at third color area forming position 95A were removed inthe same manner as the formation of the second color area. Then, adispersion comprising a blue pigment dispersed in photosensitivepolyamide resin PA-1000 (a product of Ube Industries, Ltd.) was appliedon the whole surface by spin coating, followed by pre-baking (80° C., 30minutes). Then, the whole areal exposure was carried out usingultraviolet light, from the back side of substrate 91 (FIG. 9H),followed by developing, rinsing, and post-baking to form a bluemicrofilter 95 (FIG. 9I). Thereafter, the chromium film was etched toremove it from the whole surface to provide a color filter (FIG. 9J). Aspassivation, a photosensitive polyimide resin (PI-300; a product of UbeIndustries, Ltd.) was then applied on the whole surface by spin coating,followed by pre-baking (140° C., 60 minutes). Thereafter, using aphotomask for the formation of contact hole 98A, only the top of thecolor filters was exposed to ultraviolet light to effect curing. Then,the uncured area was removed using a developing solution exclusivelyused therefor, followed by rinsing treatment using a rinsing solutionexclusively used therefor, and then post-baking (250° C., 60 minutes) toform passivation film 98. Finally, a transparent conductive film (ITO,indiumtin oxide) was formed by sputtering with a film thickness of 1,000Å, and thereafter brought into contact with the aluminum film as shownin FIG. 9K by photolithoetching, thus obtaining a low-resistivitywiring.

According to the Example described above, there was formed a colorfilter having no gap between the light-screening layer and filter layer,and having a low-resistivity electrode.

EXAMPLE 4 Preparation of laminated color filter for image pickup device

Another Example of the present invention will be described withreference to FIG. 10. This Example is a color filter for an image pickupdevice, and also a method in which the filter itself is utilized as amask used when a next color area is formed, on account of the spectralcharacteristics of the color filter.

On glass substrate 91, a chromium film as opaque film 92A was formed bysputtering with a thickness of 1,000 Å, and thereafter the chromium filmat the position at which a first color (green color) area is formed wasremoved by photolithoetching (pattern size: 30 μm²) (FIG. 10A).Thereafter, a dispersion comprising a green pigment dispersed inphotosensitive polyamide resin PA-1000 (a product of Ube Industries,Ltd.) was applied on the whole surface by spin coating with a filmthickness of 1.7 μm, followed by pre-baking (80° C., 30 minutes). Then,exposure (5,000 mJ/cm²) was carried out using ultraviolet rays, from theback side of the glass substrate 91 to cure the colored resin on theglass surface to bring it into a state insoluble to a developingsolution. Thereafter, the colored layer on the chromium film was removedusing a developing solution exclusively used therefor, and rinsed with arinsing solution exclusively used therefor, followed by post-baking(200° C., 60 minutes) to form a green microfilter as shown in FIG. 10C.As to the spectral characteristics of this green microfilter, thetransmittance was 1% at 320 nm to 380 nm at which the polyamide resinhas a sensitivity. In the formation of the next second color area also,photolithoetching was carried out in the same manner as in the formationof the first color area to remove the chromium film at the second color(blue color) area forming position as shown in FIG. 10D. Thereafter, adispersion comprising a blue pigment dispersed in photosensitivepolyamide resin PA-1000 (a product of Ube Industries, Ltd.) was appliedwith a film thickness of 1.8 μm, followed by pre-baking (80° C., 30minutes). Then, ultraviolet exposure was carried out at 3,000 mJ/cm²from the glass substrate side to cure the blue colored resin film on theglass surface, followed by developing, rinsing, and post-baking (200°C., 60 minutes). A blue microfilter was thus formed. Here, since theblue color area on the green microfilter was not cured, it was removedas a result of the developing. As to the spectral characteristics of theblue color area, the transmittance was also 1% at 320 nm to 380 nm likethe case of the green color area. The next third color (red color) areawas also similarly formed. The resulting red microfilter was formed witha film thickness of 1.6 μm (amount of exposure: 3,000 mJ/cm² ;prebaking: 80° C., 30 minutes; post-baking: 200° C., 60 minutes). Then,using a photosensitive polyamide resin (a produce of Ube Industries,Ltd.), a passivation film was finally formed with a film thickness of 1μm (FIG. 10G).

The color filter obtained in this way had no gap between thelight-screening layer and colored layer, and was able to be formed withease.

As described in the above, since, according to the present invention,the colored film is formed using the light-screening film as a mask, thelight-screening film and colored film can be precisely formed withoutany gap. Thus, in the case of display panels, no blank areas are formed,resulting in an improvement in the contrast. In the case of image pickupdevices also, no flare phenomenon is caused, and hence a sharp image canbe obtained.

The exposure is carried out from the back side, so that the adhesionbetween the substrate and colored layer is improved to make the processstable and at the same time improve the yield.

The light-screening film or layer is used as a mask. Hence, no faulting(difference in level) is caused, since there is no overlapping of thecolored film and light-screening film, so that a uniform cell gap can beobtained. Since the metal or alloy is used in the light-screening film,the wiring resistance can be lowered as a result of its connection withthe ITO film, so that it becomes possible to lessen the heat generationon the panel or the waveform dullness.

Thus, the formation of the color filter according to the back-sideexposure can bring about a good effect from the viewpoints of thestableness on the process, as well as the quality level and colorreproducibility.

In another embodiment, the present invention is a method of preparing acolor filter having a non-light-transmissive metallic film closelydisposed between color filter picture elements of respective colors on asubstrate. The steps that can be used therein comprise;

a step of forming on a substrate a plural color of colored resinpatterns comprising a colored material incorporated in a resin;

a step of providing a photoresist film by coating on the surface of thesubstrate on which the plural color of colored resin patterns have beenformed, and carrying out exposure from the back side of the substrate,followed by developing to remove the exposed area other than the coloredresin patterns;

a step of forming a non-light-transmissive metallic film on thesubstrate on which the plural color of colored resin patterns thusobtained and the photoresist film patterns provided on their tops havebeen formed; and

a step of dissolving only said photoresist film patterns to lift off themetallic film formed on the tops of the plural color of colored resinpatterns.

According to the above constitution, the colored resin pattern areaserving as the color filter picture element is utilized as a photomaskwhen the resist pattern for the lifting-off is formed, so that theresist pattern can be formed in the form well aligned with the colorfilter picture element, which gives a self-aligned form when themetallic film pattern is formed. Hence, the non-light-transmissivemetallic film can be closely provided between the color filter pictureelements of respective colors according to a simple procedure. In theinstance of image pickup devices or sensor devices that employ such acolor filter, an improvement in color reproducibility can be expected,and also the satisfactory light-screening leads to the prevention ofmisoperation of an optical device. In the instance of liquid crystaldisplay devices, an improvement in contrast and color purity can beexpected, and also it becomes possible to make them have together afunction as an electrode auxiliary wire. In addition, the wiring ofpicture element electrodes can be made with low resistivity. This iseffective for preventing signal delay in large screen display and alsopreventing display quality level from being lowered because of the heatgeneration in the cell.

Moreover, when compared with conventional ones, the device can take asuperior color filter structure with more flatness. Thus, in the typethe color filter is built in a liquid crystal display, a devicesuffering less defective orientation and having a superior displayquality level can be obtained.

FIGS. 11A to 11G constitute a flow sheet to illustrate a typicalembodiment of a process for preparing the color filter according to thepresent invention.

First, as shown in FIG. 11A, colored resin pattern 112 having a givenfilm thickness and a given pattern form is formed on substrate 111,using a first colored resin solution comprising a coloring materialdispersed in a resin.

In instances in which a photosensitive resin is used as the resin, thefirst colored resin solution is first applied with a given filmthickness on substrate 111, followed by each treatment of prebaking,exposure, developing, rinsing, and post-baking, to obtain colored resinpattern 112 having a given pattern form. In instances in which a resinhaving no photosensitivity is used, a colored resin pattern having agiven film thickness and a given pattern form is obtained by printing.Alternatively, a method can be employed in which the first colored resinsolution is applied with a given film thickness on substrate 111, andthereafter a photoresist pattern is formed on the resulting coloredresin film, followed by etching to obtain colored resin pattern 112having a given pattern form.

In instances in which a color filter comprised of two or more colors isformed, any of the above methods may be further repeated depending onwhat are required, i.e., depending on the number of the colors offilters, respectively using colored resin solutions containing coloringmaterials corresponding to the respective colors. Thus, it is possibleto form a color filter picture element comprised of three-color coloredresin patterns 112, 113, 114 as shown, for example, in FIG. 11B.

Next, on the color filter substrate thus formed, a positive photoresistis applied with a given film thickness as shown in FIG. 11C, followed bypre-baking. Then, exposure is carried out from the back side of thesubstrate, using light that affects the resulting photoresist film 115(e.g., a high pressure mercury lamp), where photoresist film 115 isbrought into photodecomposition only at the part thereof formed on theglass to make it into a form soluble to a developing solution. Becauseof the coloring materials having an absorption at the ultraviolet regionwhich are contained in respective colored resin patterns 112, 113 and114 already formed, and also because of the color characteristics of thecolor filter, the transmittance at the ultraviolet region is very low.

Hence, it is possible to utilize these colored resin patterns 112, 113and 114 as photomasks. Since, however, these colored resin patterns 112,113 and 114 have different transmission characteristics at theultraviolet region to which the photoresist has a sensitivity, dependingon the required color characteristics of the color filter, conditionsare previously so set that the light irradiated in the exposure may bein a sufficiently attenuated form at the interface between colored resinpatterns 112, 113 and 114 and the photoresist 115.

Photoresist film 115 exposed to light under the conditions set in thisway is subjected to developing and rinsing. As a result, colored resinpatterns 116, 117 and 118 with photoresist as shown in FIG. 11D can beformed on colored resin patterns 112, 113 and 114, which former arecoincident with the latter in size, in other words, have photoresistpatterns self-aligned with the latter.

Subsequently, on the substrate having thereon resin patterns 116, 117and 118 with photoresist, non-light-transmissive metallic film 119 isformed as shown in FIG. 11E. Thereafter, using a solution capable ofdissolving only the photoresist pattern, the non-light-transmissivemetallic film positioned at the tops of colored resin patterns 112, 113and 114 is lifted off, so that there can be obtained a color filtercomprising non-light-transmissive metal pattern 1110 closely disposedbetween color filter picture elements of respective colors, as shown inFIG. 11F.

Protective film 1111 can also be optionally formed on the top of thecolor filter as shown in FIG. 11G.

The resin used to form the colored resin pattern of the color filteraccording to the present invention can be arbitrarily selected fromgelatin, casein, glue, polyvinyl alcohol, polyimide, polyamidoimide,polyesterimide, polyamide, polyester, polyparaxylylene, polycarbonate,polyvinyl acetal, polyvinyl acetate, polystyrene, cellulose resin,melamine resin, urea resin, acrylic resin, epoxy resin, polyurethaneresin, polysilicone resin, and a resin obtained by impartingphotosensitivity to any of these resins, as well as commonly availablephotoresist resins. In particular, however, the resins set out below arepreferred from the viewpoints of the required performance of the colorfilter and the workability of patterns.

That is to say, preferred are polyamide resins and polyimide resins ofan aromatic type, having a photosensitive group in the molecule.Particularly preferred are polyamide resins of an aromatic type, capableof obtaining a cured film at 200° C. or less and having no specificlight absorption characteristics (those having a light transmittance ofabout 90% or more) at the visible wavelength region (400 to 700 nm).

The coloring material that forms the colored resin pattern of the colorfilter according to the present invention includes organic pigments,inorganic pigments, and dyes, on which there are no particularlimitations so long as they can obtain the desired spectralcharacteristics. In this instance, the materials can be used alone, oras a mixture of some of these. Taking account of the colorcharacteristics and a variety of performance, however, organic pigmentsare most preferred as the coloring material.

Used as the organic pigments are azo pigments such as a soluble azotype, an insoluble azo type and a condensed azo type, as well ascondensed polycyclic pigments such as an indigo type, an anthraquinonetype, a perylene type, a perynone type, a dioxazine type, a quinacridonetype, an isoindolidone type, a phthalone type, a methine or azomethinetype, and other metal complex types, or a mixture of some of these.

In the present invention, the colored resin solution used to form thecolored resin pattern is prepared by mixing the above coloring materialhaving the desired spectral characteristics in the above resin solutionin a proportion of approximately from 10 to 150%, and thoroughlydispersing the mixture by means of ultrasonic waves or a three-rollmill, followed by filtering to remove particles of a large diameter.

The colored resin pattern of the color filter according to the presentinvention is formed by applying the above colored resin solution on thesubstrate by means of a coating apparatus such as a spinner, a rollcoater and a printer, and formed into a pattern through aphotolithographic process or formed into a pattern through a printingprocess. The film thickness thereof depends on the spectralcharacteristics as desired, but should range usually from 0.5 to 5 μm,and preferably from 1 to 2 μm, in approximation.

The photoresist film formed on the colored resin pattern in the presentinvention may comprise a positive photoresist resin commonly available.In particular, it is arbitrarily selected from materials that may notcause damage such as dissolving, cracking or swelling to the coloredresin pattern disposed at the lower layer when coating is carried out,and also may readily dissolve when the metallic film is lifted off.

This photoresist film is provided by coating on the colored resinpattern in the same manner as the formation of the above colored resinpattern, using a coating apparatus such as a spinner, a roll coater anda printer. It may suitably have a film thickness of usually from 0.5 to5 μm, and preferably from 1 to 2 μm, in approximation.

Materials for the non-light-transmissive metallic film in the presentinvention can be arbitrarily selected from commonly available metallicmaterials including Cr, Al, Ni, Mo and Cu. In particular, in theinstance of liquid crystal displays, they may preferably be selectedfrom those having a smaller specific resistance in order to decrease theresistivity of the transparent electrode.

The non-light-transmissive metallic film is formed by vacuum filmforming such as vacuum deposition or sputtering of the above metallicmaterials, and may suitably have a film thickness of from 100 Å to 3 μm,and preferably from 1,000 Å to 2 μm, in approximation. The filmthickness of this non-light-transmissive metallic film may be madesubstantially equal to the colored resin pattern the color filter has,so that a remarkable effect can be seen in making flat the color filter,and, when used in liquid crystal displays or the like, it becomespossible to form a display panel causing less orientation irregularityof liquid crystal and having a superior display quality level. The filmmay further be brought into electrical contact with the transparentelectrode formed on the color filter, so that it also becomes possibleto set up a low-resistivity wiring. This serves as a countermeasure tothe signal delay in large screen display or a countermeasure to the heatgeneration in the panel, making it possible to form a panel with asuperior display quality level.

With respect to the colored resin pattern of the color filter accordingto the present invention, a protective film may optionally provided onits surface. This protective layer can be provided by a coating processsuch as spin coating or roll coating, or a vacuum deposition process,using, for example, organic resins of a polyamide, polyimide,polyurethane, polycarbonate, acrylic, epoxy or silicone type, orinorganic materials such as Si₃ N₄, SiO₂, SiO, Al₂ O₃ and Ta₂ O₃.

The color filter having the colored resin pattern as described above canbe formed on a suitable substrate. The substrate includes, for example,glass sheets, transparent resin sheets, resin films, CRT displaysurfaces or light-receiving surfaces of image pickup tubes, wafers onwhich a solid image pickup device such as CCD, BBD, CID or BASIS isformed, contact type image sensors using a thin-film semiconductor,liquid crystal display surfaces, and photosensitive materials for colorelectrophotography.

In instance in which the adhesion between the colored resin pattern andthe base substrate must be further increased, the colored resin patternmay be formed after the substrate is previously thinly coated with asilane coupling agent, or the color filter may be formed using a coloredresin comprising a silane coupling agent or the like previously added ina small amount. A greater effect can be thus obtained.

EXAMPLE 5

On a glass substrate, a green colored resin material [a photosensitivecolored resin material prepared by dispersing Lionol Green 6YK (tradename; a product of Toyo Ink Mfg. Co., Ltd.; C.I. No. 74265) in PA-1000(trade name; a product of Ube Industries, Ltd.; polymer content: 10%;solvent: N-methyl-2-pyrrolidone; pigment:polymer=1:2 mixture)] wasapplied by spin coating to have a film thickness of 1.5 μm.

Next, pre-baking was carried out on the resulting colored resin film at70° C. for 30 minutes, followed by exposure using a high pressuremercury lamp through a pattern mask corresponding with the pattern formintended to be formed.

After the exposure was completed, developing was carried out usingultrasonic waves, with a developing solution exclusively used therefor,capable of dissolving only the unexposed area of the colored resin film(a developing solution mainly composed of N-methyl-2-pyrrolidone), andthen treatment with a rinsing solution exclusively used therefor (arinsing solution mainly composed of 1,1,1-trichloroethane) was carriedout, followed by post-baking at 150° C. for 30 minutes to form a greencolored resin layer having a given pattern form.

Next, on the substrate on which this green colored resin layer having apattern form was formed, a second color, red colored pattern was formedat given position on the substrate in the same manner as the above,except that a red colored resin material [a photosensitive colored resinmaterial prepared by dispersing Irgazin Red BRT (trade name; a productof Ciba-Geigy Corp.; C.I. No. 71127) in PA-1000 (trade name; a productof Ube Industries, Ltd.; polymer content: 10%; solvent:N-methyl-2-pyrrolidone; pigment:polymer=1:2 mixture)] was used.

On the substrate on which two-color, colored resin patterns were formedin this way, a third color, red colored pattern was formed at givenposition on the substrate in the same manner as the above, except that ablue colored resin material [a photosensitive colored resin materialprepared by dispersing Heliogen Blue L7080 (trade name; a product ofBASF Corp.; C..I. No. 74160) in PA-1000 (trade name; a product of UbeIndustries, Ltd.; polymer content: 10%; solvent: N-methyl-2-pyrrolidone;pigment:polymer=1:2 mixture)] was used. Three-color, R. G. B. coloredresin patterns were thus obtained.

On the substrate having thereon the three-color, colored resin patternsobtained in this way, positive photoresist HPR-1182 (trade name; aproduct of Fuji-Hunt Electronics Technology Co.) was applied by spincoating to have a film thickness of 1.5 μm, followed by pre-baking at100° C. for 30 minutes, and thereafter the whole surface was exposed tolight using a high pressure mercury lamp from the back side of thesubstrate. After the exposure was completed, development processing wascarried out using a developing solution exclusively used therefor,capable of only dissolving the exposed area of the photoresist, followedby rinsing with water. Photoresist film patterns self-aligned andidentical in size were thus formed on the three-color, colored resinpatterns.

Next, on the substrate having thereon the three-color, colored patternswith photoresist, aluminum was vacuum deposited with a film thickness of1.0 μm. The resulting substrate was thereafter immersed in a solvent(acetone) capable of dissolving the positive photoresist to remove thephotoresist and aluminum on the colored patterns.

The color filter thus obtained had the structure in which the metallicfilms were closely disposed between the patterns of respective colors.The color filter thus obtained was also superior in the properties suchthermal resistance, light-resistance and mechanical properties.

EXAMPLE 6

Using the color filter formed in Example 5, ferroelectric liquid crystaldevice 121 having the structure as shown in FIG. 12 was fabricated inthe following manner.

Namely, on the color filter having non-light-transmissive metallic film130 between the color filter picture elements, a film of photosensitivepolyimide PI-300 (trade name; a product of Ube Industries, Ltd.) wasformed by coating with a film thickness of 1.0 μm as protective film129.

Next, exposure, developing and rinsing were carried out using a patternmask corresponding with the pattern form and coming into contact withthe non-light-transmissive metallic film, followed by post-baking toform a protective film pattern having a through-hole on thenon-light-transmissive metallic film.

Then, a film was formed by sputtering of ITO with a thickness of 1,500Å, and pattern formation was carried out to make it come into contactwith the non-light-transmissive metallic film, to obtain transparentelectrode pattern 125. Subsequently, polyimide was applied by printingwith a film thickness of 100 Å as orientation control film 127, and thena rubbing treatment was applied.

Between the color filter substrate thus obtained and an opposedsubstrate obtained in the same way, silica beads of 1.5 μm in diameterwere scattered, and both the substrates were laminated to make cellcompilement in the manner that the stripe-shaped pattern electrodesthereof may cross at right angles, followed by injection offerroelectric liquid crystal 124 and sealing, to obtain liquid crystaldevice 121.

Resulting ferroelectric liquid crystal device 121 showed a superiorcontrast and color purity. Since the transparent electrodes were made tohave a low resistance by virtue of the non-light-transmissive metallicfilm applied with the contact, the device was found excellent, withoutsignal delay and any lowering of display quality level caused by heatgeneration in the cell. Moreover, the filter with less faulting(difference in level) made it possible to obtain a liquid crystal devicehaving less defective orientation.

EXAMPLE 7

Using a thin-film transistor as a substrate, fabrication of a colorliquid crystal display device comprising a color filter formed on saidsubstrate according to the method of the present invention was carriedout in the following way.

First, as shown in FIG. 13A, ITO picture element electrode 131 with alayer thickness of 1,000 Å was formed on glass substrate 130 (tradename: 7059; a product of Corning Glass Works) to have the desiredpattern. Thereafter, on the surface thereof, aluminum was further vacuumdeposited with a layer thickness of 1,000 Å, and the resulting depositwas subjected to patterning to the desired shape according tophotolithoetching to form gate electrode 132 as shown in FIG. 13B.

Subsequently, a photosensitive polyimide was applied on the surface ofsubstrate 130 on which the above electrodes were provided, to forminsulating layer 133, followed by pattern exposure and developmentprocessing to form through hole 134 as shown in FIG. 13C. Thisthrough-hole 134 constitutes a contact between drain electrode 138 andpicture element electrode 131.

Here, substrate 130 was set at given position in a deposition chamber.Into the deposition chamber, SiH₄ diluted with H₂ was introduced tocarry out glow discharging in vacuum to deposit on the whole surface ofsubstrate 130 provided with above electrodes 131 and 132 and insulatinglayer 133, photoconductive layer (intrinsic layer) 135 comprising a-Siand having a layer thickness of 2,000 A. Thereafter, on thisphotoconductive layer 135, n⁺ layer 136 with a layer thickness of 1,000Å was laminated as shown in FIG. 13D according to a similar proceduresubsequently taken. This substrate 130 was taken out of the depositionchamber, and above n⁺ layer 136 and photoconductive layer 135 in thisorder were respectively subjected to patterning by dry etching to thedesired shapes as shown in FIG. 13E.

Next, on the substrate surface on which photoconductive layer 135 and n⁺layer 136 were provided in this way, aluminum was vacuum deposited witha layer thickness of 1,000 Å. Thereafter, the resulting aluminum depositwas subjected to patterning by photolithoetching to have the desiredshape. Source electrode 137 and drain electrode 138 were thus formed asshown in FIG. 13F.

Finally, according to the same procedure as Example 5, three-color, red,blue and green colored patterns 136a, 137a and 138a were formed as shownin FIG. 13G, corresponding with each picture element electrode 131, withthe insulating layer interposed therebetween. Thereafter, as shown inFIG. 13H, a polyimide resin as insulating film 1311 to which anorientation function was imparted was applied on the whole surface ofthis substrate to have a layer thickness of 1,200 Å, followed by curingof the resin by heat treatment at 250° C. for 1 hour. A thin-filmtransistor integrated with the color filter was thus prepared.

Using the thin-film transistor with the color filter, thus prepared, acolor liquid crystal display device was further fabricated.

More specifically, an ITO electrode layer of 1,000 Å thick was formed onone side of a glass substrate (trade name: 7059; a product of CorningGlass Works) according to the same procedure as the above, and aninsulating layer with a layer thickness of 1,200 Å, comprising polyimideresin to which an alignment function was imparted was further formed onthe electrode layer. A liquid crystal was sealed between this substrateand the previously fabricated thin-film transistor with the colorfilter, and the whole was fixed to obtain the color liquid crystaldisplay device.

The color liquid crystal display device thus fabricated had goodcharacteristics.

EXAMPLE 8

Example 7 was repeated to obtain a color liquid crystal display devicehaving the color filter formed by the method of the present invention,except that the three-color color filter was not provided on the pictureelement electrode, but instead provided on the opposed electrode.

The color liquid crystal display device thus fabricated had goodcharacteristics.

EXAMPLE 9

Example 8 was repeated to obtain a color liquid crystal display devicehaving the color filter formed by the method of the present invention,except that the three-color color filter was first formed on the opposedsubstrate and thereafter the opposed electrode was provided.

The color liquid crystal display device thus fabricated had goodcharacteristics.

EXAMPLE 10

Example 5 was repeated to obtain a color solid image pickup devicehaving the color filter formed by the method of the present invention,except that a wafer on which a CCD (charge coupled device) was formedwas used as the substrate and the three-color stripe color filter wasformed in the manner that each colored pattern of the color filter maybe disposed corresponding with each light-receiving cell possessed bythe CCD, with the insulating layer interposed therebetween.

The color solid image pickup device thus fabricated had goodcharacteristics.

EXAMPLE 11

The color filter formed in Example 5 was stuck on a wafer on which a CCD(charge coupled device) was formed, with registration so made that eachcolored pattern of the color filter may be disposed corresponding witheach light-receiving cell possessed by the CCD. A color solid imagepickup device was thus fabricated.

The color solid image pickup device thus fabricated had goodcharacteristics.

EXAMPLE 12

A color photosensor array, as schematically illustrated in a partialplan view of FIG. 14, having the color filter formed by the method ofthe present invention was prepared in the following manner according tothe process as shown in FIG. 15.

First, as shown in FIG. 15A, photoconductive layer (intrinsic layer) 145comprising an a-Si (amorphous silicon) layer was provided by glowdischarging on glass substrate 150 (trade name: 7059; a product ofCorning Glass Works). More specifically, SiH₄ diluted with H₂ to 10 vol.% was deposited on the substrate, under a gas pressure of 0.50 Torr andan RF (radio frequency) power of 10 W, at a substrate temperature of250° C. for 2 hours, to obtain photoconductive layer 145 with a filmthickness of 0.7 μm.

Subsequently, on this photoconductive layer 145, n⁺ layer 146 wasprovided by glow discharging, as shown in FIG. 15B. More specifically,using as a starting material a 1:10 mixed gas of SiH₄ diluted with H₂ to10 vol. % and PH₃ diluted with H₂ to 100 ppm and setting otherconditions same as conditions for the deposition of photoconductivelayer 145 previously provided, n⁺ layer 146 with a layer thickness of0.1 μm was continuously provided on photoconductive layer 145.

Next, as shown in FIG. 15C, aluminum was deposited by electron beamvacuum deposition on n⁺ layer 146 to have a layer thickness of 0.3 μm.Conductive layer 149 was thus formed.

Subsequently, as shown in FIG. 15D, the part corresponding to the partserving as a photoconversion area was removed. More specifically, usinga photoresist, positive type Microposit 1300-27 (trade name; a productof Shipley Co.), a photoresist pattern was formed in the desired shape.Thereafter conductive layer 149 at the uncovered area (the part providedwith no resist pattern) was removed from the surface of the substrate,using an etchant obtained by mixing phosphoric acid (an aqueous 85 vol.% solution), nitric acid (an aqueous 60 vol. % solution), glacial aceticacid and water in the proportion of 16:1:2:1, to form common electrode141 and separate electrode 140.

Next, as shown in FIG. 15E, the part serving as the photoconversionarea, of n⁺ layer 146 was removed. More specifically, after abovephotoresist Microposit 1300-2 was peeled from the substrate, dry etchingwas carried out for 5 minutes by plasma etching (also called reactiveion etching) with CF₄ gas under an RF power of 120 W and a gas pressureof 0.1 Torr, using parallel plate type plasma etching apparatus DEM-451(manufactured by Nichiden Anelva Co.). n⁺ Layer 146 at the uncoveredarea and part of the surface layer of photoconductive layer 145 werethus removed from the substrate.

In the present Example, in order to prevent implantation of the cathodematerial of the etching apparatus, a sputtering target of polysilicon (8inches; purity: 99.999%) was place on the cathode. The sample was placedthereon and the part at which SUS of the cathode material was uncoveredwas covered with a Teflon sheet cut into the shape of a doughnut. Thus,the etching was carried out in the state that the SUS surface was littleexposed to plasma. Thereafter, heat treatment was carried out at 20° C.for 60 minutes in an oven in which nitrogen was flowed at a rate of 3l/min..

Next, on the surface of the photosensor array thus prepared, protectivelayer 147 was formed in the following manner.

Namely, a silicon nitride layer as protective layer 147 was formed byglow discharging on the photosensor array. More specifically, using amixed gas obtained by mixing SiH₄ diluted with H₂ to 10 vol. % and 100%NH₃ in a flow rate ratio of 1.4 and setting other conditions same as theprocedure for the formation of the a-Si layer previously provided,protective layer 147 comprising a silicon nitride (a-SiNH) layer of 0.5μm in layer thickness was formed as shown in FIG. 15F.

On this protective layer 147 serving as a substrate, a color filtercomprised of three-color, red, blue and green, colored patterns wasformed in the same manner as Example 5, and thereafter a protectivelayer was formed. The color photosensor array device as shown in FIG.14, comprising colored patterns 136a, 137a and 138a respectivelydisposed on each photosensor, was thus formed. The numeral 130 denotes anon-light-transmissive metallic film pattern.

The photosensor array formed in the present Example had goodcharacteristics.

EXAMPLE 13

The color filter formed in Example 5 was stuck on the photosensor arrayas shown in FIG. 15F, fabricated in Example 12, using an adhesive. Acolor photosensor array was thus fabricated.

The color photosensor fabricated in the present Example also had goodcharacteristics like the one prepared in Example 12.

As having been described above, according to the present invention, inwhich the colored resin pattern for forming the color filter pictureelement is utilized as the photomask in forming the resist pattern forlift-off, the resist pattern can be formed in the form aligned with thecolor filter picture element, so that it has been self-aligned when themetallic film pattern is formed. Hence, it becomes possible to providethe non-light-transmissive metallic film between the color filterpicture elements of respective colors without a gap according to asimple method.

Thus, the image pickup device or sensor device disposed with such acolor filter can achieve;

(1) an improvement in color reproducibility; and

(2) prevention of misoperation of an optical device.

In the instance of liquid crystal display devices, superior effect canbe obtained, e.g., in respect of;

(1) an improvement in contrast and color purity;

(2) a decrease in defective orientation because of an improvement inflatness, and an improvement in display quality level, attributablethereto; and,

(3) because of the non-light-transmissive metallic film utilized as anelectrode auxiliary wire, prevention of signal delay, or prevention of alowering of display quality level, caused by heat generation in thecell.

In still another embodiment, the present invention is a method ofpreparing a color filter having a non-light-transmissive metallic filmclosely disposed between color filter picture elements of respectivecolors on a substrate. The steps that can be used therein comprise;

a step of forming on a substrate a first colored resin film comprising acolored material incorporated in a resin, laminating a photoresist filmon said colored resin film, followed by exposure and developing througha mask to carry out simultaneous patterning of the photoresist film andcolored resin film;

a step of repeating the above step several times using a colored resincomprising a coloring material having a different hue to form a pluralcolor of colored resin patterns;

a step of forming a non-light-transmissive metallic film on thesubstrate on which said plural color of colored resin patterns have beenformed; and

a step of dissolving only said photoresist film to lift off the metallicfilm formed on the tops of the plural color of colored resin patterns.

According to the above constitution, the pattern for lifting off themetallic film is also formed at the same time with the formation of acolor filter picture element, so that it gives a self-aligned form whenthe metallic film pattern is formed. Hence, the non-light-transmissivemetallic film can be closely provided between the color filter pictureelements of respective colors according to a simple procedure. In theinstance of image pickup devices or sensor devices that employ such acolor filter, an improvement in color reproducibility can be expected,and also the satisfactory light-screening leads to the prevention ofmisoperation of an optical device. In the instance of liquid crystaldisplay devices, an improvement in contrast and color purity can beexpected, and also it becomes possible to make them have together afunction as an electrode auxiliary wire. In addition, the wiring ofpicture element electrodes can be made with low resistivity. This iseffective for preventing signal delay in large screen display and alsopreventing display quality level from being lowered because of the heatgeneration in the cell.

Moreover, when compared with conventional ones, the device can take asuperior color filter structure with more flatness. Thus, in the typethe color filter is built in a liquid crystal display, a devicesuffering less defective alignment and having a superior display qualitylevel can be obtained.

FIGS. 16A to 16G constitute a flow sheet to illustrate a typicalembodiment of a process for preparing the color filter according to thepresent invention.

First, as shown in FIG. 16A, colored resin pattern 162 is formed onsubstrate 161 to have a given film thickness, using a first coloredresin solution comprising a coloring material dispersed in a resin,followed by pre-baking under suitable temperature conditions.Subsequently, a photoresist using a solvent that may not dissolve thiscolored resin is applied on this colored resin film 162, followed bypost-baking to obtain a film of two-layer structure, comprised ofcolored resin film 162 and photoresist film 163.

Next, as shown in FIG. 16B, using light (e.g., light of a high pressuremercury lamp or the like) capable of affecting both photoresist film 163and colored resin film 162 or only photoresist film 163, exposure iscarried out through a photomask 164 having a given pattern formcorresponding with the pattern intended to be formed. Then, afterdeveloping and rinsing were carried out, post-baking is carried out toobtain colored resin pattern 165 of two-layer structure with thephotoresist film disposed on its top, as shown in FIG. 16C.

In instances in which a color filter comprised of two or more colors isformed, the steps of from FIG. 16A to FIG. 16C may be further repeateddepending on what are required, i.e., depending on the number of thecolors of filters, respectively using colored resin solutions in whichcoloring materials corresponding to the respective colors are dispersed.Thus, it is possible to form color filter picture elements ofthree-color colored resin patterns 165, 166, 167 with photoresist asshown, for example, in FIG. 16D.

Next, on the color filter substrate thus formed, non-light-transmissivemetallic film 168 is formed as shown in FIG. 16E. Subsequently,lifting-off of the non-light-transmissive metallic film is carried outusing a solution capable of dissolving only the photoresist filmpositioned at the tops of the colored resin patterns. Thus, there can beobtained a color filter comprising non-light-transmissive metal pattern169 closely disposed between color filter picture elements 165a, 166aand 167a of respective colors, as shown in FIG. 16F.

Protective film 160 can also be optionally formed on the top of thecolor filter as shown in FIG. 16G.

EXAMPLE 14

On a glass substrate, a blue colored resin material capable of obtainingthe desired spectral characteristics [a photosensitive colored resinmaterial prepared by dispersing Heliogen Blue L7080 (trade name; aproduct of BASF Corp.; C.I. No. 74160) in PA-1000 (trade name; a productof Ube Industries, Ltd.; polymer content: 10%; solvent:N-methyl-2-pyrrolidone; pigment: polymer=1:2 mixture) and diluting theresulting dispersion with a cellosolve solvent] was applied by spincoating to have a film thickness of 1.5 μm, followed by pre-baking at70° C. for 20 minutes.

Next, on the resulting colored resin layer, a photosensitive polyimideresin diluted with a cellosolve solvent was applied by spin coating witha film thickness of 1.0 μm, followed by pre-baking at 80° C. for 30minutes.

The colored resin layer and photoresist layer were simultaneouslyexposed to light, using a high pressure mercury lamp through a patternmask corresponding with the pattern form intended to be formed. Afterthe exposure was completed, developing was carried out using ultrasonicwaves, with a developing solution exclusively used therefor, capable ofdissolving only the unexposed area of the colored resin film, and thentreatment with a rinsing solution exclusively used therefor was carriedout, followed by post-baking at 150° C. for 30 minutes to form a bluecolored resin film with photoresist, having a given pattern form.

Subsequently, on the substrate on which the blue colored resin layerwith photoresist was formed, a second color, green colored pattern withphotoresist was formed at given position on the substrate in the samemanner as the above, except that a green colored resin material [aphotosensitive colored resin material prepared by dispersing LionolGreen 6YK (trade name; a product of Toyo Ink Mfg. Co., Ltd.; C.I. No.74265) in PA-1000 (trade name; a product of Ube Industries, Ltd.;polymer content: 10%; solvent: N-methyl-2-pyrrolidone;pigment:polymer=1:2 mixture) and diluting the resulting dispersion witha cellosolve solvent] was used.

On the substrate on which blue and green colored resin patterns withphotoresist thus obtained were formed, a third color, red coloredpattern with photoresist was further formed at given position on thesubstrate in the same manner as the above, except that a red coloredresin material [a photosensitive colored resin material prepared bydispersing Irgazin Red BRT (trade name; a product of Ciba-Geigy Corp.;C.I. No. 71127) in PA-1000 (trade name; a product of Ube Industries,Ltd.; polymer content: 10% solvent: N-methyl-2-pyrrolidone;pigment:polymer=1:2 mixture) and diluting the resulting dispersion witha cellosolve solvent] was used. Colored patterns with photoresist, of R(red), G (green) and B (blue) three-color stripes were thus obtained.

On the substrate having thereon the three-color stripes, colored resinpatterns with photoresist obtained in this way, aluminum was vacuumdeposited with a film thickness of 1.0 μm. The resulting substrate wasthereafter immersed in a solvent capable of dissolving the positivephotoresist layer, i.e., the photosensitive polyimide pattern which wasin an uncured state, to remove the photoresist and aluminum on thecolored patterns, using ultrasonic waves.

The color filter thus obtained had the structure in which the metallicfilms were closely disposed between the mosaic patterns of respectivecolors. The color filter thus obtained was also superior in theproperties such as thermal resistance, light-resistance and mechanicalproperties.

EXAMPLE 15

On a glass substrate, a blue colored resin material capable of obtainingthe desired spectral characteristics [a photosensitive colored resinmaterial prepared by dispersing Heliogen Blue L7080 (trade name; aproduct of BASF Corp.) in an aqueous polyvinyl alcohol resin solutioncontaining ammonium dichromate as a crosslinking agent] was applied byspin coating to have a film thickness of 1.0 μm, followed by drying at90° C. for 10 minutes. Thereafter, a negative photoresist [OMR-83 (tradename; a product of Tokyo Ohka Kogyo Co., Ltd.)]. was applied by spincoating with a film thickness of 1.0 μm, followed by pre-baking at 80°C. for 20 minutes. Then, the colored resin film and photoresist filmwere simultaneously exposed to light, using a high pressure mercury lampthrough a pattern mask corresponding with the pattern form intended tobe formed. After the exposure was completed, developing was carried outusing a developing solution exclusively used therefor, and thentreatment with a rinsing solution exclusively used therefor was carriedout, followed by developing of the colored resin film, using a water/IPAmixed solution. Post-baking was then carried out at 150° C. for 30minutes to form a blue colored resin film with photoresist, having agiven pattern form.

Subsequently, R, G and B three-color mosaic colored patterns withphotoresist were formed in the same manner as the above, except that asecond color, green colored resin material [a photosensitive coloredresin material prepared by dispersing Lionol Green 6YK (trade name; aproduct of Toyo Ink Mfg. Co., Ltd.) in an aqueous polyvinyl alcoholresin solution containing ammonium dichromate as a crosslinking agent]and a third color, red colored resin material [a photosensitive coloredresin material prepared by dispersing Irgazin Red BRT (trade name; aproduct of Ciba-Geigy Corp.) in an aqueous polyvinyl alcohol resinsolution containing ammonium dichromate as a crosslinking agent] wereused.

On the substrate having thereon the three-color mosaic colored resinpatterns with photoresist obtained in this way, chromium was vacuumdeposited with a film thickness of 1,000 Å. The resulting substrate wasthereafter immersed with shaking in a solvent capable of dissolving thephotoresist to remove the photoresist and chromium on the coloredpatterns.

The color filter thus obtained had the structure in which the metallicfilms were closely disposed between the mosaic patterns of respectivecolors.

In a further embodiment, the present invention is a method of preparinga color filter having a metallic film closely disposed between colorfilter picture elements of respective colors on a substrate, comprisingthe steps of;

(a) forming conductive film patterns on the substrate;

(b) forming between said conductive film patterns, color filter pictureelements comprising a plural color of colored resin patterns in such amanner that the colored resin patterns may each have a width larger thanthe width between said conductive film patterns and may each have a gapbetween adjacent picture elements on said conductive film patterns; and

(c) applying metallic coating selectively on the conductive filmprovided at least between said plural color of colored resin patterns.Thus, the metallic film can be closely formed between color filterpicture elements of respective colors.

According to the method of preparing the color filter of the presentinvention, the conductive film pattern and color filter pattern (coloredresin pattern) to be applied with metallic coating are formedoverlapping each other in part, so that the conductive film is closelyuncovered at least between color filter patterns. Consequently,application of the metallic coating on this conductive film makes itpossible to closely form metallic films between the color filter pictureelements of respective colors.

In the instance of image pickup devices or sensor devices that employsuch a color filter, an improvement in color reproducibility can beexpected, and also the satisfactory light-screening leads to theprevention of misoperation of an optical device. In the instance ofliquid crystal display devices, an improvement in contrast and colorpurity can be expected, and also it becomes possible to make them havetogether a function as an electrode auxiliary wire. In addition, thewiring of picture element electrodes can be made with low resistivity.This is effective for preventing signal delay in large screen displayand also preventing display quality level from being lowered because ofthe heat generation in the cell.

Moreover, when compared with conventional ones, the device can take asuperior color filter structure with more flatness. Thus, in the typethe color filter is built in a liquid crystal display, a devicesuffering less defective orientation and having a superior displayquality level can be obtained.

FIGS. 17A to 17E constitute a flow sheet to illustrate a typicalembodiment of a process for preparing the color filter according to thepresent invention.

First, as shown in FIG. 17A, after a conductive film is formed onsubstrate 171, patterning is carried out to form conductive filmpatterns 172 with a gap width smaller than the width of a color filterpattern. Next, as shown in FIG. 17B, a color filter pattern 173 isformed between the conductive film patterns in such a manner that thecolor filter pattern may have a width larger than the width between theconductive film patterns and may have a gap between adjacent pictureelements on said conductive film patterns. Then, this formation of thepattern comprising a colored resin is repeated several times using acolored resing having a different hue. Thus, color filter pictureelements comprised of the three-color, colored resin patterns 173, 174and 175 are formed as shown in FIG. 7C.

Using the color filter substrate thus formed, a metal film is depositedon conductive film pattern 172 through an electrical or chemical means,while keeping selectivity between the surface of the uncoveredconductive film pattern and the color filter picture element. Thus,metallic film pattern 176 can be closely formed between the color filterpicture elements as shown in FIG. 17D. As shown in FIG. 17E, protectivefilm 177 can also be optionally formed on the top of the color filterpicture elements.

EXAMPLE 16

On a glass substrate, an ITO film was formed by sputtering with athickness of 5,000 Å, and conventional patterning was carried out toform stripe-shaped patterns each having a width of 20 μm which is largerthan the gap width 10 μm between color filter patterns.

Next, between the ITO stripe patterns on this substrate, a stripe-shapedcolor filter pattern having a width of 90 μm which is larger than thegap width between the ITO patterns was formed according to the followingprocedure.

Namely, a blue colored resin material capable of obtaining the desiredspectral characteristics [a photosensitive colored resin materialprepared by dispersing Heliogen Blue L7080 (trade name; a product ofBASF Corp.; C.I. No. 74160) in PA-1000 (trade name; a product of UbeIndustries, Ltd.; polymer content: 10%; solvent: N-methyl-2-pyrrolidone;pigment:polymer=1:2 mixture)] was applied by spin coating to have a filmthickness of 1.5 μm, followed by pre-baking at 70° C. for 30 minutes.Next, exposure was carried out using a high pressure mercury lampthrough a pattern mask corresponding with the pattern form intended tobe formed. After the exposure was completed, developing was carried outusing ultrasonic waves, with a developing solution exclusively usedtherefor, capable of dissolving only the unexposed area of the coloredresin film, and then treatment with a rinsing solution exclusively usedtherefor was carried out, followed by post-baking at 200° C. for 30minutes to form a blue colored resin film having a given pattern form.

Subsequently, on the substrate on which the blue colored resin layer wasformed, a second color, green colored pattern was formed at givenposition on the substrate in the same manner as the above, except that agreen colored resin material [a photosensitive colored resin materialprepared by dispersing Lionol Green 6YK (trade name; a product of ToyoInk Mfg. Co., Ltd.; C.I. No. 74265) in PA-1000 (trade name; a product ofUbe Industries, Ltd.; polymer content: 10%; solvent:N-methyl-2-pyrrolidone; pigment:polymer=1:2 mixture)] was used.

On the substrate on which blue and green patterns thus obtained wereformed, a third color, red colored pattern was further formed at givenposition on the substrate in the same manner as the above, except that ared colored resin material [a photosensitive colored resin materialprepared by dispersing Irgazin Red BRT (trade name; a product ofCiba-Geigy Corp.; C.I. No. 71127) in PA-1000 (trade name; a product ofUbe Industries, Ltd.; polymer content: 10%; solvent:N-methyl-2-pyrrolidone; pigment:polymer=1:2 mixture)] was used. Coloredpatterns of R (red), G (green) and B (blue) three-color stripes werethus obtained between the ITO stripe patterns on the substrate, with awidth larger than the gap width between them.

The ITO pattern of the color filter substrate thus obtained wasconnected to the negative pole, and electroplating was applied for 2minutes at a current density of 0.1 (A/cm²) in a Watts bath of 45° C. Anickel film with a film thickness of 1.35 μm was thus formed selectivelyon the uncovered ITO pattern.

The color filter thus obtained had the structure in which the metallicfilms were closely disposed between the stripe patterns of respectivecolors.

EXAMPLE 17

On a glass substrate, a Cu film was formed by sputtering with athickness of 2,000 Å, and conventional patterning was carried out toform stripe-shaped patterns each having a width of 20 μm which is largerthan the gap width 10 μm between color filter patterns.

Next, between the Cu stripe patterns on this substrate, a color filtercomprising R (red), G (green) and B (blue) three-color stripes eachhaving a width of 90 μm which is larger than the gap width between theCu patterns was formed using the same colored resin materials andaccording to the same procedure as Example 16.

On the Cu pattern uncovered on the color filter substrate thus obtained,electroless Cu plating was applied to form substantially the samepattern with the color filter pattern.

The color filter thus obtained had the structure in which the metallicfilms were closely disposed between the stripe patterns of respectivecolors.

EXAMPLE 18

An example of the present invention will be described with reference toFIG. 1.

Referring to FIG. 1, on substrate 14 comprising a glass sheet, analuminum film with a thickness of 1.0 μm was formed by sputtering,followed by patterning with a width of 30 μm. Low-resistivity electrode12 having a light-screening function was thus formed. Next,photosensitive polyimide PI-300 (trade name; a product of UbeIndustries, Ltd.) was applied on the whole surface by spin coating witha thickness of 2.0 μm, followed by mask exposure, and then patterningwas carried out so as to give a through hole with a width of 10 μm onthe aluminum pattern to provide insulating layer 13. Because of a dangerof causing disconnection of transparent electrode 11, the pattern end ofinsulating film 13 should preferably be tapered. Accordingly, it wastapered by making treatment using rinsing solution PRI-127 (trade name;a product of Ube Industries, Ltd.), in the course of the step of thepatterning of the PI-300 film. The transparent electrode 11 was providedby forming ITO into a film with a thickness of 0.1 μm by sputtering,followed by patterning with a width of 280 μm. The resistivity of theelectrode thus formed was examined to find that the resistivity per 1 cmof pattern length was about 10 Ω, which was about 1/100 when comparedwith the resistivity of about 1 KΩ of the case of only an ITO patternwith a width of 280 μm.

On the substrate shown in FIG. 1, an SiO₂ film as an insulating layer(not shown) was formed by sputtering with a thickness of 500 Å, andpolyimide was applied thereon by printing with a thickness of 100 Å asan orientation control film (not shown), which were then applied withrubbing. An opposed substrate was also formed with the sameconstitution, and silica beads of 1.5 μm in diameter were scatteredbetween the both substrates. Thereafter, they were laminated so that therubbing directions may be the same, and then ferroelectric liquidcrystal CS1014 (trade name; a product of Chisso Corporation) as theliquid crystal was injected into the cell. The cell thus prepared wasplaced between polarizers which were in a crossed nicols. While makingobservation on back light, signals were applied to the electrodes. As aresult, short (or abnormal connection) was nowhere to be found. Therewas also little waveform dullness of the applied signals to pictureelements. Moreover, the light coming through between picture elements,which causes a lowering of the display quality level, was perfectlyscreened or intercepted by low-resistivity lectrode 12, so that therewas seen a remarkable improvement in the display performance.Temperature irregularity in the cell when signals were applied to thecell for a long period of time was also examined to find that a greatimprovement was achieved as compared with a cell comprising electrodesformed only with ITO.

EXAMPLE 19

As another example of the present invention, an example in which thepresent invention is utilized in a color liquid crystal cell will bedescribed with reference to FIG. 3.

On substrate 14 comprising a glass sheet, an aluminum film with athickness of 1.0 μm was formed by sputtering, followed by patterningwith a width of 30 μm. Low-resistivity electrode 12 having alight-screening function was thus formed. As color filter 31, a coloredresin obtained by dispersing a pigment as a coloring matter inphotosensitive polyamide PA-1000 C (trade name; a product of UbeIndustries, Ltd.) was applied on the whole surface by spin coating witha thickness of 1.0 μm, followed by mask exposure, and then patterningwas carried out. This above procedure was repeated three times to form afilm having a function as an R, G and B three-color film. As insulatingfilm 13, photosensitive polyimide PI-300 (trade name; a product of UbeIndustries, Ltd.) was applied on the whole surface by spin coating witha thickness of 1.0 μm, followed by mask exposure, and then patterningwas carried out so as to give a through hole with a width of 10 μm onthe aluminum pattern. In the patterning of the PI-300 film, a treatmentusing rinsing solution PRI-127 (trade name; a product of Ube Industries,Ltd.) was made so that the pattern end was tapered. Transparentelectrode 11 was provided by forming ITO into a film with a thickness of0.1 μm by sputtering, followed by patterning with a width of 90 μm. Theresistivity of the electrode thus formed was examined to find that theresistivity per 1 cm of pattern length was about 10 Ω, which was about1/300 when compared with the resistivity of about 3 KΩ of the case ofonly an ITO pattern with a width of 90 μm.

On the substrate thus prepared, an SiO₂ film as an insulating layer (notshown) was formed by sputtering with a thickness of 500 Å, and polyimidewas applied thereon by printing with a thickness of 100 Å as anorientation control film (not shown), which were then applied withrubbing. An opposed substrate was made to comprise a substrate nothaving the color filter of Example 1, and silica beads of 1.5 μm indiameter were scattered between the both substrates. Thereafter, theywere laminated so that the rubbing directions may be the same, and thenferroelectric liquid crystal CS1014 (trade name; a product of ChissoCorporation) as the liquid crystal was injected into the cell. The cellthus prepared was placed between polarizers which were in a crossednicols. While making observation on back light, signals were applied tothe electrodes. As a result, short (or abnormal connection) was nowhereto be found. There was also little waveform dullness of the appliedsignals to picture elements. Moreover, the space between pictureelements was perfectly light-screened, so that there was a remarkableimprovement in the color purity in the color display. Not so greattemperature irregularity was also occurred in the cell when signals wereapplied to the cell for a long period of time, and there was obtained astable image quality.

As having been described in the above, the present invention makes itpossible to greatly decrease the wiring resistance at the continuouselectrode area without causing any short, when compared withconventional methods. Hence, the waveform dullness of the signalsapplied to the electrode area can be suppressed. In addition, since theheat generation in the cell can also be lessened, the temperatureirregularity in the cell can be made small. Thus, the display qualitylevel can be greatly improved.

At the same time, the light passing between picture elements can beperfectly intercepted, so that the deterioration of image quality, dueto the light coming through between picture elements, can be prevented.

We claim:
 1. A functional substrate for controlling pixels,comprising:a) a substrate; b) an insulating film provided on saidsubstrate; c) a stripe-shaped transparent conductive film provided inplurality on said insulating film; d) a strip-shaped opaque conductivefilm covered with said insulating film, arranged in parallel to saidstripe-shaped transparent conductive film, and disposed so as to cover agap formed between two stripe-shaped transparent conductive filmsadjacent to each other; and e) a contact area at which one of said twostripe-shaped transparent conductive films adjacent to each other andsaid opaque conductive film are electrically connected.
 2. Thefunctional substrate according to claim 1, wherein said opaqueconductive film is a film formed of a metal or an alloy.
 3. Thefunctional substrate according to claim 1, wherein said opaqueconductive film has a thickness of not less than 0.5 μm.
 4. Thefunctional substrate according to claim 1, wherein said insulating filmhas a film thickness set to be not less than 1.5 times the filmthickness of said opaque conductive film.
 5. The functional substrateaccording to claim 1, wherein said stripe-shaped transparent conductivefilm is provided thereon with a film having been applied with atreatment for orienting liquid crystal molecules.
 6. The functionalsubstrate according to claim 5, wherein said stripe-shaped transparentconductive film is provided thereon with a film having been applied witha treatment for orienting liquid crystal molecules, interposing anadditional insulating film.
 7. The functional substrate according toclaim 5, wherein said film having been applied with a treatment fororienting liquid crystal molecules is a film, which is subjected to arubbing treatment on the surface of a film formed of an organicinsulating material.
 8. A functional substrate for controlling pixels,comprising:a) a substrate; b) an insulating film provided on saidsubstrate; c) a stripe-shaped transparent conductive film provided inplurality on said insulating film; d) a stripe-shaped opaque conductivefilm covered with said insulating film, arranged in parallel to saidstripe-shaped transparent conductive film, and disposed so as to cover agap formed between two stripe-shaped transparent conductive filmsadjacent to each other; e) a color filter covered with said insulatingfilm and disposed at a position corresponding with said stripe-shapedtransparent conductive film; and f) a contact area at which one of saidtwo stripe-shaped transparent conductive films adjacent to each otherand said opaque conductive film are electrically connected.
 9. Thefunctional substrate according to claim 8, wherein said opaqueconductive film is a film formed of a metal or an alloy.
 10. Thefunctional substrate according to claim 8, wherein said opaqueconductive film has a thickness of not less than 0.5 μm.
 11. Thefunctional substrate according to claim 8, wherein said insulating filmhas a film thickness set to be not less than 1.5 times the filmthickness of said opaque conductive film.
 12. The functional substrateaccording to claim 8, wherein said stripe-shaped transparent conductivefilm is provided thereon with a film having been applied with atreatment for orienting liquid crystal molecules.
 13. The functionalsubstrate according to claim 12, wherein said stripe-shaped transparentconductive film is provided thereon with a film having been applied witha treatment for orienting liquid crystal molecules, interposing anadditional insulating film.
 14. The functional substrate according toclaim 12, wherein said film having been applied with a treatment fororienting liquid crystal molecules is a film, which is subjected to arubbing treatment on the surface of a film formed of an organicinsulating material.
 15. A functional substrate for controlling pixels,comprising:a) a substrate; b) an insulating film provided on saidsubstrate; c) a stripe-shaped transparent conductive film provided inplurality on said insulating film; d) a color filter having a filmthickness covered with said insulating film and disposed at a positioncorresponding with said stripe-shaped transparent conductive film; ande) a stripe-shaped opaque conductive film covered with said insulatingfilm, arranged in parallel to said stripe-shaped transparent conductivefilm, and disposed so as to cover a gap formed between two stripe-shapedtransparent conductive films adjacent to each other, wherein the filmthickness of said color filter is set to be not more than twice the filmthickness of said opaque conductive film; and f) a contact area at whichone of said two stripe-shaped transparent conductive films adjacent toeach other and said opaque conductive film are electrically connected.16. The functional substrate according to claim 15, wherein said colormicrofilter has a film thickness set to be from 0.5 time to 1.5 timesthe film thickness of said opaque conductive film.
 17. The functionalsubstrate according to claim 15, wherein said color filter has a filmthickness set to be from 0.8 time to 1.2 times the film thickness ofsaid opaque conductive film.